Method of making interconnect structure

ABSTRACT

A method of making a semiconductor device including forming a first adhesion layer over a substrate. The method further includes forming a second adhesion layer over the first adhesion layer, where the second adhesion layer is formed using an inert gas with a first flow rate under a first RF power. Additionally, the method includes forming a low-k dielectric layer over the second adhesion layer, where the low-k dielectric layer is formed using the inert gas with a second flow rate under a second RF power under at least one of the following two conditions: 1) the second flow rate is different from the first flow rate; or 2) the second RF power is different from the first RF power. Furthermore, the method includes forming an opening in the dielectric layer, the second adhesion layer, and the first adhesion layer. Additionally, the method includes forming a conductor in the opening.

PRIORITY CLAIM

The present application is a divisional of U.S. application Ser. No.13/460,279, filed Apr. 30, 2012, which claims priority of U.S.Provisional Application No. 61/617,530, filed Mar. 29, 2012, which areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to semiconductor devices and particularlyto methods of making interconnect structure.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. As technology has progressed, the demand forsmaller semiconductor devices with improved performance has increased.As feature densities in the semiconductor devices increase, the widthsof the conductive lines, and the spacing between the conductive lines ofback-end of line (BEOL) interconnect structures in the semiconductordevices also need to be scaled down.

Several approaches have been implemented in order to meet these demands.As the widths of the conductive lines reduce, the spacing between twosuccessive layers with conductive lines also reduces. The reducedspacing may therefore increase resistance-capacitance (RC) time delay.To reduce the RC time delay, low dielectric constant (low-k) materialsare being used as insulating materials, and copper is replacing aluminumfor interconnect structures. Advantages of using copper forsemiconductor device interconnects include abilities to operate fasterand manufacture thinner conductive lines because copper has lowerresistivity and increased electromigration resistance compared toaluminum. Combining copper interconnects with low-k dielectric materialsincreases interconnect speed by reducing the RC time delay, for example.

Copper interconnects are often formed using damascene processes ratherthan by direct etching. Damascene processes are typically either singleor dual damascene, which include forming openings by patterning andetching inter-metal dielectric (IMD) layers and filling the openingswith copper. However, there are some challenges in the copper damascenestructure, such as adhesion issues between the low-k dielectric materialand the underlying layer. The adhesion issues may cause film crackingand/or peeling and, therefore, result in device package qualificationfailure.

BRIEF DESCRIPTION OF THE DRAWING

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flow chart of a method for fabricating an integrated circuitdevice according to an embodiment of the present disclosure.

FIGS. 2-7 are cross-sectional views of an integrated circuit deviceduring various fabrication stages according to the method of FIG. 1according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of thedisclosure. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed between the firstand second features, such that the first and second features may not bein direct contact. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

With reference to FIGS. 1 and 2-7, a method 100 and a semiconductordevice 200 are collectively described below. The semiconductor device200 illustrates an integrated circuit, or portion thereof, that cancomprise memory cells and/or logic circuits. The semiconductor device200 can include passive components such as resistors, capacitors,inductors, and/or fuses; and active components, such as P-channel fieldeffect transistors (PFETs), N-channel field effect transistors (NFETs),metal-oxide-semiconductor field effect transistors (MOSFETs),complementary metal-oxide-semiconductor transistors (CMOSs), highvoltage transistors, and/or high frequency transistors, other suitablecomponents, and/or combinations thereof. It is understood thatadditional steps can be performed before, during, and/or after themethod 100, and some of the steps described below can be replaced oreliminated, for additional embodiments of the method. It is furtherunderstood that additional features can be added in the semiconductordevice 200, and some of the features described below can be replaced oreliminated, for additional embodiments of the semiconductor device 200.

Referring to FIGS. 1 and 2, the method 100 begins at step 102, wherein afirst etch stop layer (ESL) 220 is formed over a substrate 210. In thepresent embodiment, the substrate 210 is a semiconductor substratecomprising silicon. In some alternative embodiments, the substrate 210comprises an elementary semiconductor including silicon and/or germaniumin crystal; a compound semiconductor including silicon carbide, galliumarsenide, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Thealloy semiconductor substrate may have a gradient SiGe feature in whichthe Si and Ge composition change from one ratio at one location toanother ratio at another location of the gradient SiGe feature. Thealloy SiGe may be formed over a silicon substrate. The SiGe substratemay be strained. Furthermore, the semiconductor substrate may be asemiconductor on insulator (SOI). In some embodiments, the semiconductorsubstrate may include a doped epitaxial layer. In other embodiments, thesilicon substrate may include a multilayer compound semiconductorstructure.

The substrate 210 may include various doped regions depending on designrequirements (e.g., p-type wells or n-type wells). The doped regions maybe doped with p-type dopants, such as boron or BF₂; n-type dopants, suchas phosphorus or arsenic; or a combination thereof. The doped regionsmay be formed directly in the substrate 210, in a P-well structure, inan N-well structure, in a dual-well structure, or using a raisedstructure. The semiconductor device 200 may include a P-channel FieldEffect Transistor (PFET) device and/or an N-channel Field EffectTransistor (NFET) device. Thus, the substrate 210 may include variousdoped regions configured for the PFET device and/or the NFET device.

The first etch stop layer 220 for controlling the end point duringsubsequent etching processes is deposited on the above-describedsubstrate 210. In some embodiments, the first etch stop layer 220comprises a material including C, Si, N, or H. In some embodiments, thefirst etch stop layer 220 is formed of silicon oxide, silicon nitride,silicon carbide, silicon oxynitride, or combinations thereof. In someembodiments, the first etch stop layer 220 has a thickness of about 10angstroms to about 1000 angstroms. In some embodiments, the first etchstop layer 220 is formed through any of a variety of depositiontechniques, including, low-pressure chemical vapor deposition (LPCVD),atmospheric-pressure chemical vapor deposition (APCVD), plasma-enhancedchemical vapor deposition (PECVD), physical vapor deposition (PVD),sputtering, and future-developed deposition procedures. In somealternative embodiments, the first etch stop layer 220 is formed by athermal process. In some embodiments, the first etch stop layer 220having a thickness ranges from about 100 Angstroms to about 300Angstroms.

Referring to FIGS. 1 and 3, the method 100 continues with step 104 inwhich a first adhesion layer 230 is formed over the first etch stoplayer 220. In some embodiments, the first adhesion layer 230 includesSiOx-containing material, SiCN-containing material, SiON-containingmaterial, or combinations thereof. In some embodiments, the firstadhesion layer 230 is formed using LPCVD process, APCVD process, PECVDprocess, PVD process, sputtering, or future-developed depositionprocedures. In some alternative embodiments, the first adhesion layer230 is formed using a thermal process. In the present embodiment, thefirst adhesion layer 230 is tetraethoxysilane (TEOS). In someembodiments, the first adhesion layer 230 having a thickness ranges fromabout 100 Angstroms to about 400 Angstroms.

Referring to FIGS. 1 and 4, the method 100 continues with step 106 inwhich a second adhesion layer 240 is formed over the first adhesionlayer 230. In some embodiments, the second adhesion layer 240 is formedusing LPCVD process, APCVD process, PECVD process, PVD process,sputtering, or future-developed deposition procedures. In somealternative embodiments, the second adhesion layer 240 is formed using athermal process. In some embodiments, the second adhesion layer 240comprises a material including Si, C, O, or H. In some embodiments, thesecond adhesion layer 240 is a C-containing layer with a carbon content(C content) ratio in the base composition being greater than 13 at %(atomic percent). In some alternative embodiments, the second adhesionlayer 240 is a C-containing layer with C content ratio in the basecomposition ranging from about 15 at % to about 30 at %. In someembodiments, the second adhesion layer 240 having a thickness rangesfrom about 5 Angstroms to about 300 Angstroms.

Still referring to FIGS. 1 and 4, the method 100 continues with step 108in which a dielectric layer 250 is formed over the second adhesion layer240. The dielectric layer 250 may be a single layer or a multi-layeredstructure. In some embodiments, the dielectric layer 250 is formed usingCVD process, such as PECVD process, LPCVD process, or ALD process. Insome embodiments, the dielectric layer 250 comprises a materialincluding Si, C, O, or H. In some embodiments, the dielectric layer 250comprises elements same as to the second adhesion layer 240 but with a Ccontent ratio less than the C content ratio of the second adhesion layer240. In some embodiments, the dielectric layer 250 is a C-containinglayer with a C content ratio less than 13 at %. In some alternativeembodiments, the dielectric layer 250 is a C-containing layer with a Ccontent ratio ranging from about 10 at % and to 13 at %. In someembodiments, the dielectric layer 250 having a thickness ranges fromabout 300 Angstroms to about 2500 Angstroms.

In some embodiments, the second adhesion layer 240 and the dielectriclayer 250 are continuously formed by PECVD. In some embodiments, thesecond adhesion layer 240 and the dielectric layer 250 use at least oneprecursor, such as tetramethylcyclotetrasiloxane (TMCTS),octamethylcyclotetrasiloxane (OMCTS), diethoxymethylsilane (DEMS),diethoxyldimethylsilane (DEDMS) and other related cyclic and non-cyclicsilanes and siloxanes. In some embodiments, the precursor may be used inconjunction with an inert gas such as He or Ar and/or a reactant gassuch as H₂O, O₂, and/or CO₂. In some embodiments, the second adhesionlayer 240 and the dielectric layer 250 are continuously formed by PECVDwith the same precursor and inert gas. In some embodiments, the secondadhesion layer 240 and the dielectric layer 250 are continuously formedby PECVD with the same precursor and inert gas, but with different flowrates of the inert gas and/or different RF powers. In some embodiments,a flow rate of the inert gas for forming the second adhesion layer 240is greater than a flow rate of the inert gas for forming the dielectriclayer 250. In some alternative embodiments, the second adhesion layer240 is formed using a RF power greater than a RF power for forming thedielectric layer 250. In at least one embodiment, a flow rate of aninert gas for forming the second adhesion layer 240 is greater than aflow rate of the inert gas for forming the dielectric layer 250 and a RFpower for forming the second adhesion layer 240 is greater than a RFpower for forming the dielectric layer 250.

In some embodiments, the dielectric layer 250 is a low dielectricconstant (low-k) layer having a dielectric constant of less than 3.0 andfunctions as an inter-metal dielectric (IMD) layer. In some embodiments,the dielectric layer 250 is a low-k layer having a dielectric constantranging from about 2.5 to about 2.8. A wide variety of low-k materialsmay be employed in accordance with embodiments, for example, spin-oninorganic dielectrics, spin-on organic dielectrics, porous dielectricmaterials, organic polymer, organic silica glass, SiOF series material(FSG), hydrogen silsesquioxane (HSQ) series material, methylsilsesquioxane (MSQ) series material, or porous organic series material.

In some embodiments, the second adhesion layer 240 has a dielectricconstant substantially the same as the dielectric constant of thedielectric layer 250. In some alternative embodiments, the secondadhesion layer 240 has a dielectric constant slightly greater than thedielectric constant of the dielectric layer 250, e.g., the different ofdielectric constants is less than 2%. In some embodiments, the secondadhesion layer 240 functions as an adhesion promotion layer to improveadhesion between the dielectric layer 250 and the first adhesion layer230. Measured adhesion values that can be obtained by using the secondadhesion layer 240 are about 14 J/m² or greater. The measured adhesionvalues are higher than those in which no further adhesion layer ispresent between the dielectric layer 250 and the first adhesion layer230 for about 7% or greater.

Referring to FIGS. 1 and 5, the method 100 continues with step 110 inwhich an opening 260 is formed in the dielectric layer 250. In someembodiments, the opening 260 is formed through the dielectric layer 250,the second adhesion layer 240, the first adhesion layer 230, and thefirst etch stop layer 220. In some embodiments, the opening 260 is adual damascene opening including an upper trench section 260 a and alower via-hole section 260 b to define a contact region. Although theembodiments illustrate dual damascene opening in the dielectric layer250, the method disclosed in the present application is applicable foran embodiment having single damascene openings in the IMD layer. In dualdamascene techniques including a “via-first” patterning method or a“trench-first” patterning method, the upper trench section 260 a and thelower via-hole section 260 b may be formed using a typical lithographicwith masking technologies and anisotropic etch operation (e.g. plasmaetching or reactive ion etching). A bottom etch stop layer, a middleetch stop layer, a polish stop layer, or an anti-reflective coating(ARC) layer may be optionally deposited on or intermediately in thedielectric layer 250, providing a clear indicator of when to end aparticular etching process.

Referring to FIGS. 1 and 6, the method 100 continues with step 112 inwhich a conductor 270 is formed in the opening 260. In some embodiments,the conductor 270 is formed by a deposition process, e.g.,electro-chemical plating (ECP). In some embodiments, the conductor 270contains at least one main metal element, e.g., copper (Cu). In somealternative embodiments, the conductor 270 further contains an additivemetal element different from the main metal element, such as aluminum.

Still referring to FIG. 6, a barrier layer (not shown) may be depositedto line the sidewalls the openings 260 before forming the conductor 270.In some embodiment, the barrier layer includes Ti, TiN, Ta, TaN, otherproper material, or combinations thereof. A conductive seed layer (notshown) may be further formed over the barrier layer before forming theconductor 270. In at least one embodiment, the conductive seed layer isa metal alloy layer containing at least a main metal element, e.g.,copper (Cu). In at least one embodiment, the conductive seed layer isformed by using PVD, CVD, PECVD, LPCVD, or other well-known depositiontechniques. A chemical mechanical polishing (CMP) process may beperformed after the formation of the conductor 270 to remove the excessportions of the conductor 270 over the dielectric layer 250, thusexposing the top surface of the dielectric layer 250 and achieving aplanarized surface.

Referring to FIGS. 1 and 7, the method 100 continues with step 114 inwhich a second etch stop layer 280 is formed on the above-describedplanarized surface. The second etch stop layer 280 may control the endpoint during subsequent etching processes. The second etch stop layer280 may be formed of silicon oxide, silicon nitride, silicon carbide,silicon oxynitride, or combinations thereof, with a thickness of about10 angstroms to about 1000 angstroms, which may be formed through any ofa variety of deposition techniques, including, LPCVD, APCVD, PECVD, PVD,sputtering, and future-developed deposition procedures.

In summary, the disclosed methods and integrated circuit devices resultin improved device performance, including but not limited to, improvedadhesion between the IMD layer and the underlying layer, and thus thepeeling issue can be suppressed. Further, it can improve packagecapabilities by preventing from peeling during packaging process.

In at least one embodiment, a method of making a semiconductor deviceincluding forming a first adhesion layer over a substrate. The methodfurther includes forming a second adhesion layer over the first adhesionlayer, where the second adhesion layer is formed using an inert gas witha first flow rate under a first RF power. Additionally, the methodincludes forming a low-k dielectric layer over the second adhesionlayer, where the low-k dielectric layer is formed using the inert gaswith a second flow rate under a second RF power under at least one ofthe following two conditions: 1) the second flow rate is different fromthe first flow rate; or 2) the second RF power is different from thefirst RF power. Furthermore, the method includes forming an opening inthe dielectric layer, the second adhesion layer, and the first adhesionlayer. Additionally, the method includes forming a conductor in theopening.

In another embodiment, a method of making a semiconductor deviceincludes forming an adhesion layer over a substrate, the adhesion layerhaving a first carbon content ratio. The method further includes forminga dielectric layer over and in contact with the adhesion layer, thedielectric layer having a second carbon content ratio, where the firstcarbon content ratio is greater than the second carbon content ratio.Additionally, the method includes forming a conductor in the dielectriclayer.

A method of making a semiconductor device includes forming a firstadhesion layer over a substrate. Furthermore, the method includesforming a second adhesion layer over the first adhesion layer, whereinthe second adhesion layer comprises C, Si, or O. Additionally, themethod includes forming a low-k dielectric layer over and in contactwith the second adhesion layer, where the low-k dielectric layercomprises C, Si, or O, where an atomic percent of C in the low-kdielectric later is less than an atomic percent of C in the secondadhesion layer. The method further includes forming a conductor in thelow-k dielectric layer.

Although the embodiments have been described, it is not intended tolimit the invention to the precise embodiments disclosed herein. Thoseskilled in this technology can still make various alterations andmodifications without departing from the scope and spirit of thisinvention. Therefore, the scope of the present invention shall bedefined and protected by the following claims and their equivalents.

What is claimed is:
 1. A method of making a semiconductor device, themethod comprising: forming a first adhesion layer over a substrate;forming a second adhesion layer over the first adhesion layer, whereinthe second adhesion layer is formed using an inert gas with a first flowrate under a first RF power; forming a low-k dielectric layer over thesecond adhesion layer, wherein the low-k dielectric layer is formedusing the inert gas with a second flow rate under a second RF powerunder at least one of the following two conditions: 1) the second flowrate is different from the first flow rate; or 2) the second RF power isdifferent from the first RF power; forming an opening in the dielectriclayer, the second adhesion layer, and the first adhesion layer; andforming a conductor in the opening.
 2. The method of claim 1, whereinthe second flow rate is greater than the first flow rate.
 3. The methodof claim 1, wherein the second RF power is greater than the first RFpower.
 4. The method of claim 1, further comprising forming a barrierlayer on sidewalls of the opening in the dielectric layer.
 5. The methodof claim 4, wherein the forming the barrier layer comprises forming thebarrier layer comprising at least one of Ti, TiN, Ta, or TaN.
 6. Themethod of claim 4, further comprising forming a conductive seed layerover the barrier layer.
 7. The method of claim 1, wherein the secondadhesion layer comprises carbon.
 8. The method of claim 7, wherein thesecond adhesion layer has a carbon content ratio greater than or equalto 13 atomic percent (at %).
 9. A method of making a semiconductordevice, the method comprising: forming an adhesion layer over asubstrate, the adhesion layer having a first carbon content ratio;forming a dielectric layer over and in contact with the adhesion layer,the dielectric layer having a second carbon content ratio, wherein thefirst carbon content ratio is greater than the second carbon contentratio, and forming a conductor in an opening in the dielectric layer.10. The method of claim 9, wherein the first carbon content ratio isgreater than or equal to 13 atomic percent (at %).
 11. The method ofclaim 9, wherein forming the dielectric layer comprises forming thedielectric layer having a thickness ranging from 300 Angstroms (Å) to2500 Å.
 12. The method of claim 9, wherein the forming the adhesionlayer comprises forming the adhesion layer using a thermal process. 13.The method of claim 9, wherein forming the adhesion layer comprisesforming the adhesion layer having a thickness ranging from 100 Å to 400Å.
 14. The method of claim 9, wherein the forming the adhesion layercomprises forming the adhesion layer comprises at least one of SiOx,SiCN, or SiON.
 15. A method of making a semiconductor device, the methodcomprising: forming a first adhesion layer over a substrate; forming asecond adhesion layer over the first adhesion layer, wherein the secondadhesion layer comprises C, Si, or O; forming a low-k dielectric layerover and in contact with the second adhesion layer, wherein the low-kdielectric layer comprises C, Si, or O, wherein an atomic percent of Cin the low-k dielectric layer is less than an atomic percent of C in thesecond adhesion layer; and forming a conductor in an opening in thelow-k dielectric layer.
 16. The method of claim 15, wherein forming thesecond adhesion layer comprises forming the second adhesion layer havinga thickness ranging from 5 Å to 300 Å.
 17. The method of claim 15,further comprising forming an opening in the low-k dielectric layer. 18.The method of claim 17, further comprising forming a barrier layer onsidewalls of the opening in the low-k dielectric layer.
 19. The methodof claim 18 further comprising, forming a conductive seed layer over thebarrier layer.
 20. The method of claim 15, wherein the second adhesionlayer has a carbon content ratio greater than or equal to 13 atomicpercent (at %).